signal-to-noise: standard calculation procedure?
Posted: Fri Feb 09, 2007 5:50 pm
Hi everyone!
We are just discussing several different methods of calculating signal-to-noise ratios in chromatography (predominantly GC/MS).
baseline level = average value of local noise left and right of target peak inside 20*half-peak-width, while ignoring all data closer than 5*half-peak-width (20 and 5 = arbitrarily choosen)
noise =
a) difference between maximum and minimum value of local noise
b) standard deviation of local noise (a lot smaller!)
1) Do you know any formal requirements or standard procedures to calculate S/N ratios?
2) Do you determine the noise by method a or b? Or other? I know many people prefer standard deviation because it gives numerically better S/N. However, in spectroscopy (nmr) usually strict min-max values are used.
3) How large do you select the local noise range? How close, how far?
Obviously, the S/N is only valid for a particular acquisition method, because scan rate, scan range, dwell time and so on do influence the S/N ratio. Naturally, spikes are part of the noise. Only reproducible peaks may be ignored.
Thanks for your comments!
Kajjo
We are just discussing several different methods of calculating signal-to-noise ratios in chromatography (predominantly GC/MS).
baseline level = average value of local noise left and right of target peak inside 20*half-peak-width, while ignoring all data closer than 5*half-peak-width (20 and 5 = arbitrarily choosen)
noise =
a) difference between maximum and minimum value of local noise
b) standard deviation of local noise (a lot smaller!)
1) Do you know any formal requirements or standard procedures to calculate S/N ratios?
2) Do you determine the noise by method a or b? Or other? I know many people prefer standard deviation because it gives numerically better S/N. However, in spectroscopy (nmr) usually strict min-max values are used.
3) How large do you select the local noise range? How close, how far?
Obviously, the S/N is only valid for a particular acquisition method, because scan rate, scan range, dwell time and so on do influence the S/N ratio. Naturally, spikes are part of the noise. Only reproducible peaks may be ignored.
Thanks for your comments!
Kajjo